Instrumental sets by bands are usually just footnotes (see also the Beastie Boys' The Mix-Up). But this collection of dense headphone music feels like acreative breakthrough for Trent Reznor. A new-media showpiece like Radiohead's In Rainbows, Ghosts I-IV is a self-released kiss-off to Reznor's former label, Universal, which he ditched last year after months of public feuding. You can download part of it (free) or all 1.8 hours ($5), or order it in various physical configurations (the $300 limited edition has already sold out to fanatics). Musically, Ghosts rewards close attention. The touchstone is Brian Eno's headier work: the murky instrumentals on Another Green World, the angular rhythm collages of My Life in the Bush of Ghosts. But Reznor's own hyper-detailed language defines the set: heaving synthesizers, doleful piano, alien-insect noises. There are animalistic contributions by King Crimson guitarist Adrian Belew, so the apocalyptic ambience frequently rocks. And since it's licensed with Creative Commons (the organization that redefines copyright to encourage noncommercial artistic sampling), Ghosts' awesome sound palette may soon enter the digital-music lingua franca — a gift that should keep on giving.

“Let My Love Open the Door”

A peppy, hopeful love song, "Let My Love Open the Door" became a U. S. Top Ten hit for Pete Townshend in 1980, anchored by the kind of repeating synthesizer figures that he'd used in some of the Who's recordings in the previous decade. Although Townshend brushed the song off as "just a ditty" in Rolling Stone shortly after its release, in 1996 he revealed it was about love of the holiest sort. "It's supposed to be about the power of God's love," he remarked. "That when you're in difficulty, whether it's major or minor, God's love is always there for you."